Get Back in That Hole, Partner

When you reach the Old Bacchus House along New Austin's southern border, you'll find that Seth has adapted remarkably well to the impending apocalypse. He's not particularly helpful, but he does suggest that you cleanse three more graveyards. This will require you to travel most of the way across New Austin.

The three graveyards labeled on your map are Coot's Chapel near Armadillo, Odd Fellow's Rest near the Ridgewood Farm, and the church in the abandoned town of Tumbleweed. Like the graveyard in Blackwater, cleansing these requires you to incinerate the coffins scattered around each chapel with the Torch. You'll receive small amounts of ammo for each coffin you burn, and the local zombie population will wake up as you do so.

At Coot's Chapel, the "boss" undead isn't anything special, but there are a couple of Bruisers mixed into the population.

Odd Fellow's Rest has a couple of Bolters and Bruisers interred within it, and the boss, Pete Turner, is an ordinary undead.

Finally, the graveyard at Tumbleweed is the hardest to get to, mostly because the area around Gaptooth Ridge is some of the roughest country in the game. Undead animals and large mobs of zombies are everywhere, and Tumbleweed itself is some kind of infinite undead generator. Cleaning out the graveyard involves fighting several Bolters, a couple of Bruisers, a Retcher, and a bunch of normal undead led by the sharply-dressed Jimmy Saint.

Once all three graveyards have been cleansed, head back to Seth's house at the Old Bacchus Place. Following that moment of crippling terror, Seth points you towards Mexico.